96 Again, We have complete confidence that sacred ministers will be even more careful than others in faithfully observing the prescriptions of Canon Law, (98) which make the pious use of the Sacrament of Penance, which is so necessary for the attainment of sanctity, obligatory at certain specified times; and that they will treat those urgent exhortations which this same predecessor of Ours made "with a sorrowful soul" on several occasions (99) with the supreme veneration and obedience they deserve.
Source: Sacerdotii Nostri Primordia (Vatican.va)